REPORT ON THE RADIOLARIA. 1195 



Subfamily 1. Sethopilida, Haeckel, 1881, Prodromus, p. 431. 



Definition. — T r i }) o c y r t i d a, with the basal mouth of the shell open (vel Dicyr- 

 tida triradiata aperta). 



Genus 534. Dictyophimus,^ Ehrenberg, 1847, Monatsber. d. k. preuss, 

 Akad. d. Wiss. Berlin, p. 53. 



Definition. — S e t h o p i 1 i d a (vel Dicyrtida triradiata aperta) with three complete 

 thoracic ribs, prolonged into three solid divergent feet on the peristome. Cephalis with 

 an apical horn. 



The genus Dictyophimus, comprising many common species, may be regarded as 

 the common ancestral form of all Sethopilida, and therefore also of the whole family of 

 Dicyrtida. The cephalis bears an apical horn, and the thorax three ribs, which are 

 prolonged over the open mouth into three solid feet. Dictyophimus may be derived 

 either from Eusceniuni or Peridium (Archiperida), or from Tripospyris (Zygospyrida), 

 or from Plectaniscvs (Plectanida), by development of lattice-work between the three 

 terminal feet, which therefore become thoracic ribs. 



Subgenus 1. Dictyophimium, Haeckel. 



Definition. — Shell smooth or rough, -ndthout prominent spines on the edges of the 

 three thoracic ribs. (Commonly one single horn on the cephalis.) 



1. Dictyophimus spharocephalus, n. sp. (PL 57, %. 10). 



Shell smooth, with a deep collar stricture, separatiug two joints of nearly equal size. Cephalis 

 subglobular, rough, with a stout pyramidal horn of half the length, and regular, circular, hexagonally 

 framed pores. Thorax nearly three-sided prismatic, smooth, with three stout, little divergent or 

 nearly parallel ribs, which are prolonged into conical subvertical feet half as long. Thoracic 

 pores irregular, roundish. 



Dimensions. — Cephalis 0-08 long, O'OS broad ; thorax O'OS long, 0-08 broad. 



Habitat. — Western Tropical Pacific, Station 225, depth 4475 fathoms. 



2. Dictyophimus tripus, Haeckel. 



Dictyophimus tripus, Haeckel, 1862, Monogr. d. Eadiol., p. 306, Taf. vi. fig. 1. 



Shell with a slight collar stricture, separating two joints of slightly differen't size. Cephalis nearly 

 eUipsoidal, large, with a slender conical horn of the same length. Thorax truncate three-sided 



■ Dictyophimtis = ^et goljlet ; oiV-ti/oi/ Jsiui:. 



